Add selection orompt Search (#1289)

* Add selection prompt search as you type

* Fix small bug

* Simplify

* Simplify

* Remove spacebar as a selection prompt submit key

* Trigger CI

* Update src/Spectre.Console/Prompts/SelectionPrompt.cs

Co-authored-by: Martin Costello <martin@martincostello.com>

* Simplifty Mask method

* Handle multi-selection prompt better

* Update API naming

* Address feedback

* Add some tests

* Remove whitespace

* Improve search and highlighting

* Add test case for previous issue

* Add extra test case

* Make prompt searchable

---------

Co-authored-by: Martin Costello <martin@martincostello.com>
Co-authored-by: Patrik Svensson <patrik@patriksvensson.se>

examples/Console/Prompt/Program.cs

@@ -110,6 +110,7 @@ namespace Prompt
             {
                 fruit = AnsiConsole.Prompt(
                     new SelectionPrompt<string>()
+                        .EnableSearch()
                         .Title("Ok, but if you could only choose [green]one[/]?")
                         .MoreChoicesText("[grey](Move up and down to reveal more fruits)[/]")
                         .AddChoices(favorites));